So far as known to the inventor, previous pilots made by others have been formed of metal and had open ended nozzles. These nozzles tended to melt and were subject to peening in the highly corrosive environment of a natural gas flare.
In one particular pilot of the prior art, there is provided a flame front generator. Fuel and air is pre-mixed and supplied to one end of a pipe, the other end of which includes a nozzle placed adjacent the top of a flare stack. The fuel-air mixture is ignited and travels along the pipe to the nozzle. Such an arrangement is troublesome in that if the pilot goes out, all the fuel-air mixture in the pipe must be blown out before the pilot can be re-lit. The resulting delay and difficulties in establishing the precise fuel-air mixture required to create the flame front (which is dependent on the humidity) makes this pilot unreliable.
The present invention is intended to provide an improvement in pilots for flare stacks, and in particular is intended to provide a continuous pilot that may be re-lit instantaneously.
In one aspect of the invention, therefore there is provided a novel nozzle for a flare stack pilot, in which the nozzle is made of ceramic or like material, has plural openings extending around the nozzle, and has a new framing and sparking system. Electrodes spaced to form a spark gap are disposed adjacent one of the openings in the nozzle, preferably a constricted opening in an axial end of the nozzle. The use of a ceramic nozzle avoids the deterioration of the metal commonly found with metal nozzles, and using a constricted end, with circumferential openings for the flow of gas into the nozzle, assists in preventing downdrafts into the nozzle from blowing out the pilot light.
There is therefore proposed in one embodiment of the invention a nozzle for a pilot light, the nozzle being formed of a housing defined by an encircling wall, preferably forming a cylinder. The housing has first and second ends, at least the second end being open for the flow of gas into the housing, and a plurality of openings formed in the encircling wall and extending radially through the encircling wall. The openings are disposed circumferentially around the housing between the first and second ends and is made of material characterized by being resistant against breakdown in a sour gas environment at temperatures at least less than 1200.degree. C., preferably 98% by weight alumina ceramic.
The nozzle is held by a cage, which includes a base plate having a central aperture and first and second sides, a tube extending into the aperture from the first side of the base plate and fixed to the base plate, and plural retainer members extending from the base plate and enclosing the nozzle. The end opposed to the base plate is preferably a constricted open end to allow but partially obstruct the flow of gas into the nozzle.
In a further embodiment, there is provided a pilot for a flare stack, the pilot including a nozzle such as the one described above made of electrically non-conducting material. The nozzle has an encircling wall defining an interior cavity and at least an open end, with preferably two open ends. A plurality of openings are formed in the encircling wall and extend radially through the encircling wall, the openings being disposed circumferentially around the encircling wall. A gas conduit is connected into the interior cavity of the nozzle. A cage confines the nozzle and has means for attaching the cage to a flame stack. A first electrode extends at least linearly adjacent the first open end of the nozzle, and a second electrode extends about the nozzle and is spaced from the first electrode to form a spark gap between them. A source of electrical power is connected to one of the first and second electrodes.
The first electrode preferably forms part of the cage for the nozzle, and forms a ring about a first open end of the nozzle. The first open end is preferably constricted to obstruct the flow of gas through the first open end. The second electrode extends in a plane adjacent the first electrode. The first electrode is preferably grounded.
The invention provides in another aspect of the invention an igniter for a flare stack including a first probe having a first tip end that may move in normal wind conditions in a substantially planar surface, a second probe having a second tip end, one or both of the first and second tip ends being extended at least in a ring in a plane parallel to the planar surface, the first tip end being disposed adjacent the second tip end; whereby upon movement of the first tip end, a substantially constant gap is formed between the first tip end and the second tip end. In a still further aspect of the invention, one of the first and second tip ends extends in more than one dimension to form a planar surface.